1. Field of the Invention
The present invention relates to a communication system and method for sending and receiving electronic mail between communication terminal devices via a server and digital data network.
2. Description of the Related Art
In recent years, computer communication networks such as Internet are developing. This is because, for example, the computer communication networks are advantageous in error correction and a user can communicate with computers in a user's own country and even in other countries by only bearing a communication expense (line usage fee and provider fee) from a user's computer (terminal device) to a provider. The provider is a company that provides communication service between the user's computer and computer network. The user generally contracts a nearby provider through a digital network such as ISDN (Integrated Services Digital Network).
When the user connects his or her terminal device to a server computer of the provider on ISDN network to attempt receiving (downloading) electronic mail addressed to himself or herself, the user must bear a communication cost even if there is no electronic mail addressed to himself or herself since the user's computer is once connected to the server computer. One example of such conventional communication systems is disclosed in Japanese Patent Application, Laid-Open Publication No. 8-331358.